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The present invention relates to a method for treatment of brain tissue, and, in particular, a method for treating brain tissue using cryotreatment.
Disorders of the brain, such as epilepsy, tumors, cysts, or Parkinson""s disease, are conventionally treated by drug therapy. Yet drug therapy carries a significant risk of complications and side effects, and must be carefully monitored over a period of time to find the precise dosage required. Additionally, drug therapy can cause potentially life-threatening low blood pressure conditions and side effects. Further, brain disorders such as stroke (hemorrhagic or embolic), vasospasm, and ischemia pose additional difficulties. Another option, angioplasties, while providing some relief, are not always useful and are difficult to position inside the complex structure of the brain. Moreover, many patients do not respond to such treatment and thus surgical excision of a target region of brain tissue, or xe2x80x9cfocusxe2x80x9d, becomes necessary.
Normally, only the portions of the brain responsible for the transmission of abnormal activity are targeted for resection or sectioning. Yet in all cases, there is a risk of removing small amounts of normal brain tissue which may be critical to normal functions such as speech, sensory perception, or motor control. Known conventional techniques which employ heat or hyperthermia can cause significant peripheral damage by denaturing proteins in the brain, leaving waste substances behind leading to serious complications. To prevent such surgical sequellae, mapping methods have been developed to be used in conjunction with any procedure. Prior to surgery, extensive mapping using electroencephalography (EEG), magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), or other means can generate a detailed map of the brain and is used to identify the target focus. Once the area is adequately mapped, and a target focus identified, treatment can proceed wherein such focus is ablated as desired.
However, current methods are still imperfect as complications can readily occur. Part of the reason is that the conventionally used ablation tool itself is xe2x80x9cabsolute.xe2x80x9d Once the target focus site is identified, the surgical excision is performed and the procedure is final. No correction is made for mapping errors, nor does it allow for continuous or xe2x80x9cprogressivexe2x80x9d monitoring of the ablation process. Known ablation tools do not allow for enhanced mapping in conjunction with, and as an integral part of, the ablation process.
Therefore, it is desirable to have a method for treating brain tissue that is minimally invasive and does not cause peripheral damage to healthy tissue. Furthermore, it is desirable to provide an ablation method to treat brain tissue which is progressive, may be used in conjunction with known mapping techniques, allowing for continuous mapping during the ablation process.
A method is disclosed for treating brain tissue, including the steps of providing a surgical tool having a cryotreatment element, mapping a target region of said brain tissue, identifying a first focus for cryotreatment, positioning said cryotreatment element proximate said first focus, and treating said first focus with said cryotreatment element.
Another method is disclosed for treating a target region of brain tissue, including the steps of providing a catheter having a flexible body having at least one lumen, proximal and distal end portions, said distal end portion enclosing a thermally transmissive cryochamber in fluid communication with said at least one lumen, positioning said catheter to dispose said cryochamber proximate said target region of brain tissue, injecting a refrigerant fluid flow into the at least one lumen in said catheter body, and expanding said refrigerant fluid flow inside said cryochamber.
Still another method is disclosed for cooling brain tissue, including the steps of providing a thermally transmissive cryochamber in fluid communication with a flow of fluid refrigerant therein, positioning said cryochamber proximate said brain tissue, injecting said fluid refrigerant into said cryochamber to flow therein, and changing the thermodynamic properties of said fluid refrigerant flow inside said cryochamber to absorb heat from said brain tissue.
Finally, a method is disclosed for cryotreatment of brain tissue, comprising the steps of identifying a conduction path in a region of said brain tissue, and applying cryotreatment to said region of brain tissue to create a lesion in said tissue and to form a conduction block along a said conduction path.